Tunable laser devices are known in the art. For example, there are electromechanically tuned lasers, for example the HP8168 tunable laser, available from Hewlett-Packard, Inc., Palo Alto, Calif. the United States. Such laser devices include a gain section and a mechanically adjustable, external, reflective grating. Wavelength tuning is performed by mechanically adjusting the angle of the external grating until the desired wavelength is reached.
Electrically tunable distributed Bragg lasers are also known in the art. Such laser devices may include a gain section, a phase section and a Bragg reflector section. The phase section is typically integrally formed with the gain and Bragg reflector sections, on a single laser chip, and the length of the phase section is not greater than 200 micrometers. At this length, the laser has a single longitudinal mode. Tuning of the laser is performed by adjusting the bias voltages of the phase and/or gain and/or Bragg reflector sections. Although electrical tuning is generally convenient, such laser devices have a number of drawbacks. A primary disadvantage is that tuning of such devices is not continuous, due to mode hopping, and there are substantial gaps in the tuning range. Additionally, such devices have a limited wavelength tuning range. Experiments with electrically tunable Bragg laser are described, inter alia, in the following publications:
F. Delorme and G. Alibert, "Reliability study of 1.55 micron DBR lasers grown in three MOVPE steps", Optical Fiber Conference, 1997, Dallas, Tex., paper FC2; PA1 F. Delorme, S. Slemkes, G. Alibert, B. Rose and J. Brandon, "Butt-jointed DBR laser with 15 nm tunability grown in three MOVPE steps", Electronic Letters vol. 31, pp. 1244-1245, July, 1995; PA1 T. L. Koch, U. Koren and B. I. Miller, "High performance tunable 1.5 micron InGaAs/InGaAsP multiple quantum well distributed Bragg reflector Lasers", Appl. Phys. Lett. vol. 53, pp. 1036-1038, September 1998; and PA1 S. Murata, I. Mito and K. Kobayashi, "Over 720 Ghz (5.8 nm) frequency tuning by a 1.5 micron DBR laser with phase and Bragg wavelength control regions", Electronic Letter vol. 23, pp. 403-404, April 1987.